Hair removal devices rely on the photothermolysis principle to destroy hair follicles. This hair removal procedure often requires raising the temperature of the treated area until reaching the desired damage effect. These procedures could often prove to be painful.
Therefore, there is a great need to develop a device for hair removal that heats the hair follicle to a degree sufficient to cause damage while keeping the level of pain minimized.
Low-fluence light pulses from a coherent light source such as a laser or an incoherent light source such as from a flash lamp have been used for hair removal treatment, as described in U.S. Pat. No. 8,950,406. That patent describes delivering a series or plurality of these pulses rapidly to the treated area. The hair follicle is damaged while minimally raising the thermal energy of the epidermis. The skin temperature found to damage the hair follicle is about 45° C. while keeping the temperature of the epidermis in a range from about 42-50° C. However, this light-based technology is melanin-based, and thus only dark colored hair follicles absorb the energy of the light source.